Above-average 'dead zone' expected in Gulf of Mexico this summer

LOS ANGELES - An above-average "dead zone" is forecast to threaten fish and other marine life in the Gulf of Mexico this summer, according to the US National Oceanic and Atmospheric Administration (NOAA).

The area is projected to span approximately 5,827 square miles (about 15,000 square km), roughly the size of the US state of Connecticut, said the agency in a press release on Thursday.

Dead zones, or hypoxic areas, are regions with low oxygen levels that can kill fish and other marine life. These zones occur annually, primarily due to nutrient pollution from human activities, particularly in urban and agricultural areas along the Mississippi-Atchafalaya watershed.

This year's forecast size is based on the US Geological Survey's data on river discharge and nutrient loading in the Mississippi-Atchafalaya watershed for May, according to NOAA.

When excess nutrients, like nitrogen and phosphorus, enter the Gulf of Mexico via the Mississippi-Atchafalaya River Basin, they cause an overgrowth of algae. When the algae die and decompose, they consume oxygen as they sink to the ocean floor, leading to hypoxic conditions.

These low oxygen levels force marine animals, such as fish and shrimp, to leave the area. Exposure to hypoxic waters can also affect fish diets, growth rates, reproduction, habitat use, and the availability of commercially important species like shrimp.

Reducing the impact of these hypoxic events remains a priority for NOAA, said Nicole LeBoeuf, assistant administrator for NOAA's National Ocean Service.

"These forecasts are designed to provide crucial data to scientists, coastal managers, and communities, and are used as guideposts in the development of planning actions," she said in the release.

Efforts to mitigate dead zones involve addressing nutrient pollution at its source, primarily by reducing runoff from agricultural and urban areas.